In order to design improved seat hardware for automobiles, it is helpful to determine the bending and torsional characteristics of the seatback portion of a seat assembly. By so doing, one is able to establish more readily seat deformation characteristics and criteria which can improve occupant retention on the seat and define biomechanical responses when subjected to rear-end impact loads. In addition, the bending and torsional characteristics of a seatback portion could also provide preliminary data for dynamic sled tests investigating the characteristics of seats modified to include energy absorbing or occupant retention concepts.
One type of seatback load applying device used currently for determining the bending and torsional stiffness of a seatback utilizes a hydraulic cylinder which applies a load through the upper cross member of the seatback. In other words, the load is applied only at a single point and at the highest cross member of the seatback. One problem with this form of load applying device is that it does not provide a real world scenario in which the loading of the seatback can occur initially at a lower portion of the seatback and afterwards at higher levels as an occupant moves in the seat.